Conventional syringes each include a barrel having an open proximal end and an opposed distal. A cylindrical wall extends between the ends and defines a substance retaining chamber. An elongate tip projects from the distal end of the syringe barrel and includes a narrow passage which communicates with the substance retaining chamber of the barrel. A plunger may be inserted into the open proximal end of the syringe barrel for sliding fluid-tight engagement with the cylindrical chamber wall. Sliding movement of the plunger in a distal direction urges fluid in the chamber through the passage in the tip. Conversely, sliding movement of the plunger in a proximal direction draws fluid through the passage in the tip and into the chamber of the syringe barrel.
Conventional syringe barrels typically are made of plastic or glass. Glass exhibits lower gas transmissivity than plastic. Thus, glass syringe barrels are used for medications that are particularly susceptible to interaction with ambient gases. Glass syringe barrels also are preferably used for medications that are pre-filled into the syringe barrel and stored for a considerable period of time prior to use.
Such syringes may further include a needle assembly with a needle cannula having a proximal end, a pointed distal end and a lumen extending axially therethrough. The needle assembly also includes a hub which is engageable with mounting means on the syringe barrel for selectively placing the lumen of the needle cannula in fluid communication with the passage through the tip of the syringe barrel. One prior mounting means includes a luer collar disposed in spaced concentric relationship around the tip of the syringe barrel. The luer collar includes an array of threads for threaded engagement with corresponding structure on the hub of the needle. For example, the luer collar may include an array of internal threads which are engageable with projections extending outwardly from the hub of the needle cannula. Syringe barrels formed from plastic may have the luer collar unitarily molded therewith. However, glass syringe barrels may not be easily formed with a unitary luer collar. Thus, glass syringe barrels and some plastic syringe barrels may have a separately formed luer collar securely mounted to the tip of the syringe barrel. The luer collar may rely upon a slip fit interengagement, a snap fit or other such secure mounting engagement around the tip of the syringe barrel.
Medications that are pre-filled into a syringe barrel must be sealed to prevent contamination or loss of the medication. Seals also prevent health care workers from being needlessly exposed to medications. The prior devices have included stoppers or closures mounted over the tip at the distal end of the syringe barrel to prevent leakage and to avoid contamination of the medication. Prior tip caps have been formed from elastomeric material frictionally and/or resiliently retained in engagement with the tip of the prior syringe barrel. The prior tip cap may be removed from the syringe tip shortly prior to usage of the syringe. The hub of the needle assembly may then be securely engaged with the luer collar or other mounting means adjacent the exposed tip of the syringe barrel. For example, the needle hub may be threadedly engaged within the luer collar such that the lumen of the prior needle cannula communicates with the exposed tip of the prior syringe barrel.
Prior elastomeric tip caps on the ends of pre-filled syringe barrels generally perform well. However, the resiliently and/or frictionally engaged type tip cap may be accidentally disengaged from the tip of the syringe barrel in response to inadvertent forces imposed thereon or due to dimensional changes or instability of the elastomeric seal. Additionally, the vacuum or suction effect created as the prior elastomeric tip cap is removed from the tip of the syringe barrel can lead to the loss of medication and unnecessary personal contact with medication that the tip cap is intended to avoid. Additionally, the prior elastomeric tip cap provides no evidence of tampering or misuse of a pre-filled syringe.
Thus, there has been a need for a syringe, as well as a tip cap, which would eliminate the problems and limitations associated with the prior syringes discussed above, most significant of the problems being evidence of tampering or misuse of a pre-filled syringe.